Immediate post-operative rehabilitation of the knee or hip joint is desirable following many surgical procedures, including total joint replacement or joint reconstruction, to restore the joint to its full range of motion. Effective rehabilitation requires controlled movement of the knee or hip joint as soon as possible after surgery without bearing weight on the joint or placing a substantial force load on the joint. As rehabilitation progresses, the range of joint movement can be increased and force loads can be applied to the joint.
U.S. Pat. No. 3,612,042 to Fry discloses a manually driven device for exercising a hip joint of a bedridden patient. The device has an overhead support structure positioned above the bed of a reclining patient. A rigid bar is mounted to the support structure by a swivel assembly engaging the midpoint of the bar above the affected hip joint. The swivel assembly is configured to permit rotation of the bar in a horizontal plane, but not in a vertical plane. A pair of slings hang from the distal end of the bar above the leg and a handle is provided at the proximal end of the bar for manual operation of the device. In operation, the fully-extended leg is placed in the slings and suspended from the distal end of the bar. The proximal end of the bar is manually rotated in a horizontal plane toward the longitudinal axis of the patient's body, thereby rotating the distal end away from the longitudinal axis. Horizontal rotation of the bar in this manner increases the abduction angle of the leg to provide abduction exercise of the hip joint.
Although the device of Fry provides effective abduction exercise of the hip joint, it has no utility for flexion and extension exercise of the hip or knee joint. Other devices have been developed for flexion and extension exercise of the knee joint termed continuous passive motion devices. Such devices, as for example disclosed in U.S. Pat. No. 4,974,830 to Genovese et al., mount the leg on a support structure while the knee joint is driven through alternating flexion and extension by applying a motorized external force to the knee joint across a mechanical pivot point. Continuous passive motion devices require careful anatomical alignment of the support structure with the leg and strict monitoring of the motorized external force loads applied to the leg joints to prevent post-operative injury to the joint during rehabilitation thereof. Furthermore, such devices are relatively complex and cumbersome to operate and maintain, as well as costly to produce.
As such, it is an object of the present invention to provide a device for rehabilitation of a leg joint, and in particular a knee or hip joint, which is relatively inexpensive to produce, and relatively simple to operate and maintain. It is another object of the present invention to provide a device for rehabilitation of the knee or hip joint which is readily adaptable to different size users without requiring careful anatomical alignment of the device with the knee joint. It is a further object of the present invention to provide a device that can passively apply a controlled manual force to the knee or hip joint for range of motion exercise thereof with a relatively low risk of injury to the joint. It is another object of the present invention to provide a device that can actively apply a desired degree of the user's own leg muscle force to the knee or hip joint for range of motion exercise of the joint without bearing weight thereon.